Load rheostat



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United States Patent 'O LOAD RHEOSTAT Michael M. Crep, Eveleth,

Original application October 28 1954, SerlalNo. 465,388. Divided andthis application November-29 `1956,-Serial N o. 625,159

1 Claim. (Cl. 201--48) This invention relates to .apparatus .forapplying apredetermined load to a storage battery 4for .the purpose oftesting the capacity or condition thereof or for controlling aheavy-current load such yas an .arc-welding .operation or aconductor-capacity test.

This is a division from my vcopending .application Serial No. 465,388,led October v28, 19.54 forfCurrent Control Apparatus for TestingBatteries or the Like.

The object of the invention is to provide a testing or current-controlapparatus applicable generally to batteries of various voltages andcapacities for determining their ampere-hour capacity at a givenVdischarge .rate or making a periodic test of internal physicalcondition Iby noting the voltage drop after a short-time overload.

A further Objectis to provide a unitary or "package .tester which iscompact, of relatively light weight .and readily portable so it can lbe.moved to .the .location of the battery to be tested.

A still further object is to lprovide a heavy-duty controller forregulating the output from a battery to .a highcurrent load.

Another object is to provide a simple arrangement and circuit of loadresistors for close current control vand la motor-driven fan or blowerfor supplying cooling air thereto.

A complete understanding of the invention may be obtained from thefollowing detailed description and explanation which refer to theaccompanying drawings illustrating the present preferred embodiment. Inthe drawings:

Figure l is a front elevation of myinvention;

Figure 2 is a transverse section therethrough taken along the plane ofline II--II of Figure 1 showing parts in elevation;

Figure 3 is a sectional view taken along the plane of line III-III ofFigure 2, with parts in elevation;

Figure 4 is a plan View of the control and indicating panel with partsomitted;

Figure 5 is an elevation `of the interior of a louver box or ventilatoroutlet;

Figure 6 is a side view thereof; and

Figure 7 is a circuit diagram.

Referring now in detail to the drawings, and for the present to Figuresl to 4 particularly, the apparatus of my invention comprises avertically elongated case 10 made up of angle-iron frame 11 havingfront, back and side sheathing plates 12, 13 and 14, respectively,secured thereto. The case is provided with feet 15 at the bottom,rearwardly extending handles 16 at the top and a wheeled carriage 17 atthe back whereby it may be moved as a hand truck from one location toanother and then stood on its feet in erect position. A fan or blower 18mounted on back plate 13 adjacent carriage 17 and driven by a motor 18a,delivers a stream of cooling air through an lopening 13a to the lowerportion of the interior of the case. As shown in Figure 3, side plates14 extend upwardly only about half-way of the height of the case. Louverboxes 19, shown in detail in Fig- 2,883,498 `Patented Apr. l21, 1959ures 5 and .6, overlie the remaining portions fof thesides rof the'case.Each `louver box `includes-"side.and'topwalls `segmental wiper disc 28ljournaled Von.thegpanelisadapted to enter between the fingers of Athecontacts and electrically connect together all 4the contacts'it engagesin successive positions -as `it .is turned clockwise. Ahandle y29secured to the disc but insulated therefrom projects outwardly through-an opening-30m the .lfrontplate 12. A

portion of the `periphery 'of ldisc v28 is yof reduced diameter to clearcontacts 27 and is provided with ,positioning notches 31. These notchescooperate with a yieldable spring-urged detent arm 32 `pivoted to .frame11 and lhaving a roller 33 Vof insulation lengaging the notched edge ofthe disc. A dog 34 fsecured to the disc determines the zero position ofthe handle vand disc von counterclockwise -movement thereof. Four ofIthe resistors 25, designated 25a through 25d, Aare connected tocontacts 27 as shown in Figure 7 to constitute with disc 28 ahigh-capacity controller for applying heavycurrent loads to a batteryfor test brother purposes.

A sloping indicating and control panel 35 forms the top `of case 10 -andhas fan `ammeter 36 and voltmeters 37 through 42 mounted thereon. Ablock 43 oiinsula- .tion carried beneath thepanel 35 by bolts 35a hascontact buttons 44 thereon adapted to be engaged .successively by acontact .finger v45. The .n'geris mounted on a .shaft -46 journaled inthe block normal thereto and extending upwardly through an opening 47 inpanel 35. An vactuatinghandle-48 is secured to the `projectingupper endof the shaft. The remaining two resistors 25, 4designated 25e and 25j,are connected to buttons 44 as :shown in Figure 7, to constitute acontroller for applying anormal load to a battery to determine itsampere-hour capacity. A .scale 49 on panel 35 and a pointer on 4shaft`46 vcooperating therewith, indicate the position Iof finger-45.

A shunt 50 for ammeter 36 is mounted on a bracket 51 depending fromframe 11 and a series resistor 52 for the fan motor is similarly mounted(see Figure 2). A switch 53 is mounted on panel 35 for shunting resistor52 when desired.

For applying test or other loads to a battery, the various circuitelements described above are connected as shown in Figure 7. The batteryis represented at 55. Spring clips 56 and exible leads aord detachableconnections therefor and a similar connection 57 is provided for eachvoltmeter, adapted to be secured to a terminal of each cell of thebattery in order.

Resistors 25a and 25b, 25e and 25d are grouped in pairs, the resistorsof each pair being interconnected by jumpers S8 and 58a. Jumpers 58 areconnected to common conductors 59 and 60 both of which are connected toa negative bus 61. A positive bus is shown at 62. The remaining jumperconnections 58a are extended to contacts 27 in succession. Theseconnections cause the total resistance connected in series with theshunt 50 and battery 55 to decrease in regular steps as wiper disc 28 isadvanced from the oi position to engage successive contacts. Thus agradually increasing current is drawn from the battery.

The remaining resistors 25e and 25j have taps connected to buttons 44 sothat advancing the finger 45 con- -rent while the remaining resistorsare used Yto make tests of voltage drop on short-time overload or tocontrol the heavy current required for welding or testing conductorlcapacity.' t

With the circuits as shown in Figure 7, if it is desired to make anampere-hour capacity test, it is only neces- 'saryI to advance finger 45until ammeter 36 indicates 'ratedtcu-rrent output and then measure thetime during lvvhich'fthe battery delivers-the prescribed current.Y If itis 'desired to make a test of the internal condition of thebattei'yeither before or after charging, disc 28 is adva'cediunt'il the'prescribed overload current (150% of 'S.A.E. -20 min. "discharge rate)is indicated on the ammeterv and the drop in the voltage of individualcells after apredetermined time v(30 sec.) is observed. It will beunderstood that individual cells or any group of cells may 4be tested-in either Way, as well as the battery asa whole. l '"vFor'weldingf'thepositive clip 56 is attached to the electrode,f the positive terminal ofthe battery is connected tothefwo'rkfland'disc 28Yis advanced to causethe desired fc'ur'ren't l-iiow when the electrode is brought in contact`vvitllthe work. For testing the current capacity of a conductor, 'alength thereof is connected in the same man- -ne'l as' the'welding loadand disc 28 adjusted to give the proper current value.

Fan motor 18a is connected across the flexible leads connected to clips56 and in series with a resistor 52. Itl is vthus energized as long asthe clips are in position on the battery terminals. For batteries ofhigher voltage, i.e., 18 volts or more, resistor 52 is left in circuitby lopening switch 53. For batteries of lower voltage,

switchl 53 is closed. In either case the fan is driven to cool resistors25 at all times when a battery is connected, regardless of the positionsof disc 28 and linger 45.

Voltmeters 37 through 42 are connected in series so that one lead fromeach to the positive terminal of successive cells gives an indication ofthe individual voltvages of the several cells.

' It will be apparent that the invention is characterized by numerousadvantages. It provides a compact, unitary, portable device of sucientcapacity to test heavy-duty batteries either over a prolonged period atnormal load or by a short-time overload. It also facilitates control ofheavy-current loads such as welding and conductorcapacity testing. Thedesired load may easily be applied by advancing either disc 28' orfinger 45 until ammeter 36 indicates the proper current. The resistorconnections and fan permit heavy current to be drawn and the energythereof safely dissipated. No power source other than the battery beingtested is needed for the fan motor. The device permits an indication ofthe condition of the battery plates and insulating separators to beobtained quickly without` opening up the cells. The mobility of theapparatus permits it to be easily moved to the location of`the ybatteryto be-tested.

The invention may be used for the discharge of batteries to be taken outof service temporarily, as well as the balancing of the state of chargeof various cells showing different specific gravity of the electrolyteby partially discharging those cells having the higher reading.

' Although I have disclosed herein the preferred ernbodiment of rnyinvention, I intend to cover as Well any lchange or modilication thereinwhich may be made without departing from the spirit and I claim: l In aAcurrent controller, the combination with a pair scope of the invention.

'of resistors connected together at their ends and having taps spacedtherealong, jumpers connecting corresponding taps of the two resistorsand a common conductor connected to` alternate jumpers, of contactsdisposed in .an arc and a segmental conducting disc rotatable to engageand connect all the contacts sucecssively, the remaining jumpers'beingconnected to said contacts in order, wherebyv rotation of said disc toengage the contacts successively,' places a gradually increasing load ona current source when one terminal thereof is connected to the disc andthe other to said common conductor, a second pair of resistors similarlyprovided with taps, jumpers and a common conductor connected to that ofthe first pair of resistors, the remaining jumpers of the second pair ofresistors being connected successively to contacts alternating withthose to which the remaining jumpers of the rst pair of resistors areconnected.

References Cited in the iile of this patent .UNITED STATES PATENTS'2,501,813 v Franklin Mar. 2s, 195o 2,561,140 Schaefer Jury 17, 19512,760,146 Wnentchik Aug. 21, 1956 2,774,934 Giu/enflammer Dec. s, 1956

